Spirits are residual form of energy that can attach to the aura of a person and causing mild fever, drowsiness or even vomiting. That is all about most cases of genuine spirit possession that I have seen so far. The above mentioned type of spirit possession can be cured by consuming blessed holy water or taking flower bath once or twice.
The forms of spirit possessions as depicted in the movies maybe done consciously or unconsciously. I have seen both cases of man-made possessions:
If you would ask who on this earth would fake a spirit possession case? Then, you may be surprised to learn that people especially the weak ones would fake possession to attract attention, sympathy, company and financial help.
When the possession is fake, then the more exorcism ritual done; the more dramatic the condition of the person to be possessed becomes. Let me tell you a real story:
About a decade ago, I was told by my friend that a lady known as May was possessed by 10 demonic entities. He later brought me to the lady's place to see if I could help. When we arrived at the possessed May's place, there was already a group of church members singing hyms and praised the Lord to cast out demonic forces within the said lady.
My pal and I didn't want to interrupt. So we just stoodby and watch. May was seen sitting in a chair with her limbs held fast by four persons while a lady stood in front of May pressing her right hand on May's head.
The lady shouted out loud: "In the name of our Lord, speak out your name!"
"Eeer... XYZ, SOP, ABC..."
May continued to struggle virgously and screamed in agony...
And after another rounds of prayer, the lead lady told May's father that the demons inside May were too strong to be cast out that round, they would return to hold another round of prayer one week later.
Just at this time, my eyes inadvertently veered at May's face and found her face showed a sense of peace and relaxed, which was a total contradiction to her appearance just a few seconds ago. Then I saw many presents, foods and clothing supposedly brought by those church members to help May and her father.
After the crowd left, my pal introduced me to May's father and boasted about my ability. As my pal was talking, May's face suddenly became distorted again. Moan and groan was heard came out from May's throat.
So both gentlemen stopped talking and looked at me expecting me to perform miracles. At this point, I thought something wasn't quite right with May. So I decided to play a trick:
Me: "Who are you?"
May: "XYZ... I wanna kill you!"
Me: "Why kill me? Demons like to make love... Let's take off our clothes and make love together..."
Suddenly May gave me a slap that almost hit my face. Her face flushed and turned red.
Almost immediately the one who stood in front of me became a shy lady once more!
"Gotcha!" I burst out in laughter and pushed my astonished friend out of May's house.
Of course, if the person is having a history of mental depression or hallucination or drug taking; then proper professional help should be sought seriously speaking.